The present invention relates generally to the field of battery terminals. More specifically, the invention relates to a battery terminal having an undercut feature about which a plastic container or cover flows upon molding to form a seal.
In general battery terminals are utilized as an interface between a sealed battery container and an external device seeking electrical power. In sealed batteries that contain liquid electrolyte the battery terminal must be configured to prevent leakage of electrolyte to ensure the battery will not fail prematurely when utilized. To prevent leakage of electrolyte it is common to provide a plurality of annular rings extending around the battery terminal which is then embedded in the wall of a container body or cover. However, even with rings about the battery terminal embedded within a plastic container it is still possible for electrolyte to leak through the container along a flash line that is caused during the cold forming or casting manufacturing process.
One attempt to minimize the leaking of electrolyte is to form an undercut on one or more of the rings as disclosed in U.S. Pat. No. 6,644,084 entitled Method and Apparatus for Manufacturing a Battery Terminal with Undercut Rings, issued to Bernard Spiegelberg and assigned to the owner of the instant application.
Once the terminal is embedded within the plastic housing, the entire container is dipped within an electrolyte bath to fill the interior volume of the housing. Some of the electrolyte seeps between the battery terminal and the plastic housing at the interface on the top of the housing. Specifically, electrolyte may seep between the interface between the plastic and the battery terminal. The electrolyte that seeped within the interface then seeps outward over time and changes the color of the external portion of the terminal. Although, this small volume of electrolyte is not leaking from within the sealed battery, it none the less darkens the battery terminal. The darkened battery terminal suggests that there maybe a leak between the battery terminal and plastic housing. As a result the battery terminal seal will be viewed as defective.
An additional problem with the manufacture of batteries is the need to use an adhesive to fully seal a lead battery terminal within a plastic cover or housing. One such attempt to eliminate the need for an adhesive is solved by the use of undercut rings as disclosed in U.S. Pat. No. 6,644,084. It would be desirable to eliminate the need to use adhesive as well as to eliminate the need to form rings.
It would be desirable to eliminate electrolyte from being trapped between the terminal and housing as the housing is being filled. It would further be desirable to provide a leak proof feature between the terminal and housing at both the interface between the lower portion of the terminal within the housing and the upper portion of the housing proximate the top surface of the housing. It would also be desirable to eliminate the need to form rings about the battery terminal and still provide a sufficient seal to provide a seal between the battery terminal and plastic housing or cover.